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1. ELECTRONIC COMPONENTS, , INTRODUCTION . :, The application of electronic science is widely growing due to large ee ual sees, components. Most of the success in electronic field over electricity is a due 7 age oi, characteristics of components, like nonlinear performance, ie iene th it basic, the electronic components. Without studying theoretically and practically thet an, construction and function, it is difficult to understand working of circuits. In this c : er, most of the common electronic components has been discussed up to a certain extent, i,, that students can understand basic action of the components, their ratings, colour code, systems and desired practical knowledge of component testing., , 1.1 CLASSIFICATION OF COMPONENTS ., , If you observe carefully any electronic circuit, you can be a little surprised; there are only, five varieties of the electronic components. Actually the circuit may appear complicated, because of number of different components, but each type belongs to any of these five, types. Electronic components which are now available in the market are classified into, two groups (A) Passive Components (B) Active Components., , , , PEEGIRONIT COMPONENTS, (A) Passive Components - (B) Active Components, , Fixed ., , 1) Resistors Electron Tubes Semiconductors, Variable | : ', Fixed t * . TJ, , 2) C t : :, , ) Capaci IS Variable Vacuum Tubes Gas Diodes Transistors, , Diode filled, , Air core Triode Tubes, , 3) Inductors Iron core, , Ferrite core, Fig. (1.1)
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131, , , , Electronic Components, , The above chart shows classification of components in brief. Detail classification can be, le al, made in different ways., , (a) Passive Components: Since this category belongs to inactive functions of the, component, these components do not have capacity to amplify the voltage or to rectify, supply. Therefore, they are called as “passive components’. However, without these, components assembly of electronic circuit is not possible. Resistors, Capacitors and, Inductors are called as passive components., , (b) Active Components: Since these components are capable of performing active, functions like amplification, ‘rectification and switching, they are’ called as “active, components”. Hundreds of active components are now manufactured they can be, classified in to. two broad groups (i) Electron tubes like Diode, triode and (ii), semiconductor devices like diode, LED, Transistor etc. Electron tubes are now rarely, used because they are outdated., , 1.1 RESISTORS, , In electronic circuits Copper, Aluminum materials are known as conductors, having, negligible resistance. Other materials like paper, ceramic, are known as insulators,, having very high resistance. Other materials like carbon with certain value of resistance, is used from very low to high value between conductor and an insulator.. These materials, are called as resistors, The value of resistance is measured in Ohm (Q). Resistance is the, opposition to the “flow of electrons or simply opposition to the electric current., Resistance is required in electronic circuits to limit the current, to drop the voltage and, to divide the voltage. In combination with capacitor, it is used as filter or it can be used, , to achieve the time delay., , TYPES OF RESISTORS, Resistors may be classified as (a) Fixed Resistors and (b) Variable Resistors., , The resistors are manufactured by either of three basic. materials-carbon composition,, wire wound and metallized. These materials differ in their resistance material. According, to their construction, resistors may be fixed or variable. Fixed resistors, whose resistance, value is constant while the resistance value of variable resistor is adjustable between the, specified range: The symbol of fixed and variable resistors is shown in fig (1.2), , —) I, —w00——— —yln— ww, , Fixed : Variable Variable, , , , Fig. (1.2) Symbols of Resistor
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132 . Electronic Components, , (a) FIXED RESISTORS, , In this category, resistance has only one value and most of the structure of this type is, cylindrical in shape that has two wire leads or terminals. Iixed resistors can be classified, into three types according to the material used, (1) Carbon types —> (a) Carbon composition type,, (2) Wire wound type, (3) Metal film type, , Let us see the construction and special features of each in brief., , (b) Carbon film type., , (1) Carbon Composition Resistors, , These resistors are widely used in electronic circuits. Carbon composition resistor’ s, value is available from 1Q to about 20 MQ and typical power ratings are 1/8 W to 2W., Specialty of these resistors is low cost and small size. (Most of the resistors available in, your laboratory are carbon composition type). These resistors are manufactured by, mixing granules of carbon with binding material. This cylinder is molded in a cylindrical, form as shown. Fig. (1.3) shows the construction and different wattages of resistors., Tinned copper wire leads are inserted in the two ends and structure is sealed with nonconducting coating. The cost of resistor depends on its wattage and.not on the value of, , resistor., ep AS, nee, , V/2W, , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , Carbon composition, , , , L, 2w V4 WwW, , Fig. (1.3) Carbon Composition Resistor, , Colour Coding of Carbon Resistor, , Another specialty of carbon resistor is its colour code system, used to indicate its, value and tolerance, where tolerance specifies the maximum deviation of the actual value, on both sides. Hence it is expressed in terms of % . e.g. if a resistors of 100 Q value and, its tolerance is + 5 % , this means the resistor value may be in the range of 95 Q to 105, Q. If it is £10% then its value is in between maximum 110 Q to minimum 90 Q and so, on. If user wants very close value to 100 2 then he will select + 5% tolerance. Resistor, , of + 5% tolerance indicates that its value may not be exactly 100 Q it lies in between +, 5% of the actual value. Tolerance is specifying % error in actual value.
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134 . Electronic Components, , Sa EEE ener a Rll), , (2) Wire Wound Resistors, , Wire wound resistor is used where high current control is required as well as, , where stable and accurate value of resistor is required. A wire wound resistor js, , manufactured by wrapping a length of special-resistive wire like nichrome or mangenin, , around an insulating core of ceramic. The end of wire is attached to metal contacts,, , “which are inserted in the core. After wire is wound, the whole structure is coated with, enamel containing powdered glass and then heated to produce coating, this is known as, vitreous enamel coating. It is required to protect the resistor and to dissipate the heat,, , Typical values are available in fraction of ohms to 100 KQ. Power rating is from 5 W to, , 200 W., The drawback of this resistor is its big size and higher values are not possible due, to its size., Resistive wire, , , , , Enamel coating Terminal f, , : Fig.(1.5) Wire wound Resistor \, , Speciality : Big in size, More power handling capacity. Colour Code System is not used, Range : Fraction of Q to 100 KQ and power rating 5 W to 200 W., , , , , , , , , , , , , , , , , , , , , , Comparison:, , | Carbon Composition Resistor Wire Wound Resistor |, 1. Carbon granules are used. A resistive wire like nichrome is used. |, 2. Tolerance is +2% to-20% More precision type because tolerance is very low. |, 3. Wide range of resistance. Available in low values only. / : |, , | 4. Low power ratings. _| High power ratings. / |, , | 5. Color code system is used. | No color code. oo, , |_6. Small size & low cost. | Big size & high cost. |, , (B) VARIABLE RESISTORS, , Variable resistors are commonly called as rheostats, electronic circuit, small variable resistors are called as “, potentiometer name probably originated from the work, , resisiors are’nocmally used in'radity ar-audig €quipment for volume control, and contrast, and brightnéss control in TV sets. According to materi - » and, , : : aterial uséd these resistors are, classified into two types esis, , (1) Carbon type and (2) Wire wound type, , In low current circuit like in, potentiometer or pots”. This, “Potential divider”. Variable
